The widespread use of photovoltaic (PV) systems mounted to homes, businesses and factories is generally considered to be a desirable goal. Several factors are believed to be critical to the acceptance of PV systems, in particular by the individual homeowner. Primary among the factors are ease of installation, cost and aesthetics. One way of addressing both cost and aesthetics has been through the use of photovoltaic shingle assemblies. One way such shingle assemblies address the cost issue is by being used as a replacement for conventional shingles, preferably using similar mounting techniques. The aesthetic issue has begun to be addressed by the use of photovoltaic assemblies in the form of shingles or roofing tiles having similar configurations and dimensions as conventional shingles or roofing tiles, and by the use of appropriate colors and reflecting characteristics to help provide an aesthetically pleasing visual appearance to the roof or other building surface. See, for example, U.S. Pat. No. 5,112,408. However, photovoltaic shingle systems have not been as widely accepted as hoped-for because 1) PV mounted integrally with the building roof as shingles operate at higher temperatures, causing a reduction in PV electrical output due to an inverse relationship between temperature and PV efficiency, as well as increasing the temperature of the roofing surface; 2) the same higher operating temperatures approach or exceed the upper limit of the warranted PV operating temperature and serve to shorten the useful life of the PV shingle; 3) some products call for electrical connections between shingles to be made under the roof deck, requiring holes to be drilled through the roof deck which increases the likelihood of water leaks; 4) there has been poor aesthetic match of PV shingles in conjunction with the non-PV areas of the roof; 5) some PV shingles have been limited to amorphous silicon PV technology, which suffer from a low operating efficiency; and 6) the value of the PV shingle has typically been limited to the electrical output of the PV plus the material value of displaced conventional shingles when the product displaces conventional shingles.
One of the concerns with using photovoltaic modules on a building roof is that in the photovoltaic module is a potential fire ignition source and also a potential source of fuel for a fire within the building. In recognition of this, some manufacturers install a Class A rated roof system, such as asphalt shingles, beneath Class C rated PV modules to meet building code requirements. Other manufacturers have used PV module constructions that have glass on both sides of the laminate (rather than Tedlar on the back side) to achieve this rating. However, this approach has not been used on PV modules that are intended to integrate with conventional concrete roofing shingles. Neither of these approaches prevents radiant heat transfer from the PV module to the roof.
See U.S. Pat. Nos. 3,769,091; 4,001,995; 4,040,867; 4,189,881; 4,321,416; 5,232,518; 5,575,861; 5,590,495; 5,968,287; 5,990,414; 6,061,978; 6,111,189; 6,584,737; and 6,606,830. See US Patent Application Publication Numbers US 2001/0050101; US 2003/0154680; US 2003/0213201; US 2003/0217768; and US 2004/0031219. See also EP1035591A1; and WO96/24013.